1. Field of the Invention
The present invention relates to a liquid crystal display module, and more particularly, to a liquid crystal display module including light emitting diodes (LEDs).
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCDs have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
In general, an LCD includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD. Thus, the LCD displays images by varying the intensity of the induced electric field.
The LCD includes a backlight unit to supply light to a liquid crystal panel. Recently, as a light source of the backlight unit, light emitting diodes (LEDs) are widely used.
FIG. 1 is a cross-sectional view illustrating an LCD module according to the related art.
Referring to FIG. 1, the LCD module 1 includes a liquid crystal panel 10, a backlight unit 20, a main supporter 30, a top case 40 and a bottom case 50.
The liquid crystal panel 10 includes first and second substrates 12 and 14 facing each other, and a liquid crystal layer therebetween.
The backlight unit 20 is located below the first substrate 12. The backlight unit includes a LED assembly 29, a reflector 25, a light guide plate 23 and at least one optical sheet 21.
The LED assembly 29 is configured along a side of the light guide plate 23. The LED assembly 29 includes a plurality of LEDs 29a emitting white light and a LED printed circuit board (PCB) 29b. The plurality of LEDs 29a are mounted on the LED PCB 29b. 
The reflector 25 is located on the bottom case 50, the light guide plate 23 is located on the reflector 25, and the at least one optical sheet 21 is located on the light guide plate 23.
The main supporter 30 surrounds the liquid crystal panel 10 and the backlight unit 20. The main supporter 30 is coupled with the top case 40 covering peripheral portions of the liquid crystal panel 10 and the bottom case 50 covering a bottom portion of the backlight unit 20. Through assembling the above components, the LCD module 1 is completed.
Further, polarizing films 19a and 19b are attached onto bottom and top surfaces, respectively, of the liquid crystal panel 10.
A position of the LED assembly 29 is fixed through a method such as an adhesion and the like so that the LEDs 29a face a light entering surface of the light guide plate 23. To do this, a side portion of the bottom case 50 is bent upward, and the LED assembly 29 is attached onto the bent side portion through an adhesive such as a double-sided adhesive tape. This structure may be referred to as a side top-view type.
In this structure, light emitted from the LEDs 29a is incident on the light entering surface of the light guide plate 23 then is refracted in the light guide plate 23 toward the liquid crystal panel 20. This light along with light reflected by the reflector 25 is processed into high-quality uniform plane light while passing through the optical sheet 21 then is supplied to the liquid crystal panel 20.
Although not shown in the drawings, a soldering portion is formed at an outer surface of an end portion of the LED PCB 29b. A FPC (flexible printed circuit) to supply power for the LED PCB 29b is coupled with the LED PCB 29b through the soldering portion. However, since the soldering portion contacts a side portion of the bottom case 50 made of metal, a short circuit defect is caused.
To prevent the short circuit defect, a method using an insulating tape is proposed. FIG. 2 is a view illustrating the case that a first insulating tape is attached onto the soldering portion in the LCD module according to the related art, and FIG. 3 is a view illustrating the case that a second insulating tape is attached onto a portion of the bottom case of the LCD module according to the related art.
Referring to FIG. 2, a first insulating tape referred to as a Kapton tape is attached onto the soldering potion. Alternatively, referring to FIG. 3, a second insulating tape referred to as a Teraoka tape is attached onto a portion of the bottom case 50 corresponding to the soldering portion.
However, processes of attaching the first and second insulating tapes are all performed by a worker. Accordingly, difference of the process time is caused according to the worker's skill, and caused is difference of rate of product error due to the insulating tapes coming off in assembling process after attaching the insulating tapes.
Further, the first and second insulating film are expensive, thus production costs increase.
Further, the soldering portion, the bottom case 50 and the insulating tape therebetween forms a capacitor. Accordingly, high capacitance may occur, and this causes a short circuit or spark. Accordingly, the LED PCB 29b is caused to be damaged, or the FPC 70, which is connected to the LED PCB 29b via the soldering portion, is caused to be damaged, as shown in FIG. 4, and thus the backlight unit is malfunctioned.
Further, as time goes by, the insulating film becomes worn because of frequent friction between the insulating film and both of the soldering portion and the bottom case 50, and insulating property of the insulating film is thus reduced. This causes a short circuit defect.
Further, due to the insulating film, thickness of the soldering portion increases. Accordingly, after assembling process, the light guide plate is caused to be pushed out. Thus, light leakage occurs at a display region near the LED.